This invention relates to a vehicle antilock brake control device and more particularly, to a vehicle antilock brake control device suited for pressure reduction mode operations.
In a conventional antilock brake control device, the device begins a control mode (pressure reduction mode) to release brake fluid pressure of the wheel cylinder when the device senses an indication of a wheel being locked. The indication of a wheel being locked can be determined from one of several situations, such as when the amount of wheel slip of a particular wheel goes beyond a predetermined threshold value or when a deceleration (i.e., negative acceleration) of the wheels goes beyond a predetermined threshold value. When the device senses such an indication, pressure reduction mode begins and the amount of time for pressure reduction is determined with the maximum target rate of pressure reduction speed based on the amount of wheel slip and the wheel deceleration, and then fluid pressure of the wheel cylinder is reduced.
However, the above-described conventional devices have the following disadvantages.
A relationship which determines the rate of pressure reduction from the amount of wheel slip and the wheel deceleration requires repeating a large number of experiments to obtain the necessary data to determine the relationship and requires an enormous amount of time and expense. Also, the relationship determined as such tends to lack logical consistency. Procedures to put this relationship into practice tend to include many complicated problems which can be very difficult.